1. Field of the Invention
This invention relates to a synthetic resin backed carpet. In one of its aspects, the invention relates to a process for injection molding a thermoplastic backing to a carpet layer. In another of its aspects, the invention relates to a synthetic resin backed carpet and to a vehicle dashboard panel formed of a synthetic resin backed carpet. In another of its aspects, the invention relates to the above injection molding process, whereby the process utilizes a low pressure gas-assist.
2. Description of the Related Art
Adhesives have long been used to bond a layer of carpet to a carpet mat base, wherein the base is an injection molded synthetic resin. These products have been domestically used as bath mats and throw rugs. Other applications for such products have included uses in connection with vehicles: door panels, vehicle dashboards, side wall trims, head liners, and floor mats. Other applications for such products can also be contemplated such as for office furniture wall panels.
It has been found that much adhesive must be used to bond the carpet mat base to the carpet layer. Also, a huge initial cost for production of such products is incurred since an applicator, dryer, conveyor and a press must be purchased to carry out the application and bonding operations. The cost of the adhesive and the bonding operations account for the greater part of the overall cost of the finished product. Applying the right amount of adhesive without fouling the edges of the mat base and bonding it to the carpet in registry requires highly skilled personnel. Furthermore, most adhesives deteriorate due to heat or moisture and will not exhibit high adhesion strength over an extended period. Another factor that reduces the bonding strength of the adhesive is the uneven surface of the back side of the carpet which causes a gap between the mating surfaces. For these reasons, the strength of the bond formed between the mat base and the carpet by an adhesive is smaller than that achieved by fusion of the resin of which the mat base is made.
In an ever-increasing effort to improve adhesion between the carpet mat base and the layer of carpet and reduce the costs of adhering the carpet to the carpet mat base, inventors have found that the carpet can be placed inside an injection molding apparatus in order to injection mold the carpet to the base. By injection molding the carpet to the base, adhesion can be greatly improved because the carpet is fused to a portion of the synthetic resin base. Also, the costs of producing the finished product have been greatly reduced because there are no material costs for the adhesive and because the precise application and bonding operations by skilled personnel are no longer required. U.S. Pat. No. 4,491,556 issued Jan. 1, 1985 to Fujii et al. discloses one such injection molding process.
Although the process disclosed in the Fujii et al. patent has in many respects proved preferable to the conventional means for adhering a carpet layer to a synthetic resin backing, the process is undesirable in many respects. For instance, because a very high injection pressure of the synthetic resin is used, tearing and matting of the carpet layer often occur. Secondly, high injection pressures tend to cause problems with "bleed through," which is a penetration of the entire carpet layer in certain spots by the synthetic resin.
Thus, there is a need for a process which is capable of injection molding a layer of carpet to a synthetic resin backing. The process must produce a layer of carpet which is firmly adhered to a synthetic resin, while not causing tearing or matting of the carpet layer. Furthermore, bleed through of the synthetic resin into the carpet layer must be eliminated.